1. Field of the Invention
The present invention relates to an information processing apparatus for recording, reproducing or erasing information along a track groove provided on a recording medium, utilizing a physical phenomenon generated when a probe needle is maintained close to a specimen.
2. Related Background Art
Recent development of the scanning tunnel microscope (hereinafter abbreviated as STM) enabling direct observation of the electron structure on and in the vicinity of a specimen surface, utilizing the physical phenomena such as tunneling phenomenon generated when a probe needle is maintained at a small distance to the specimen [G. Binnig et al., Helvetica Physica Acta, 55,726 (1982)] has allowed measurement of the real space image with a high resolving power, both in the monocrystalline and amorphous substances. Also STM has the advantages of enabling observation with a low electric power consumption, without damage to the specimen by the current, and functioning not only under high vacuum but also in atmospheric condition or in solution, and is expected to be usable in various academic and research applications. Also its spatial resolving power of the atomic or molecular level has attracted attention in the industrial field, and, for example the Japanese Patent Application Laid-Open Nos. 63-161552 and 63-161553 proposed its application to a record/reproducing apparatus, employing a thin film of organic compounds containing .pi.-electron system or chalcogenide compounds as the recording layer.
Such information process apparatus is generally designed to record information on the surface of a specimen by a certain electrical method while scanning said surface with a probe needle, and to reproduce the recorded information by measuring a physical phenomenon, such as the tunneling current generated by the close positioning of the probe needle and the specimen. For achieving smooth recording and reproduction of information, it is necessary to arrange information with certain regularity on the specimen. It is therefore desirable to record and read the information along a track groove, and, in an information record/reproducing apparatus, the addition of a tracking system is required.
Tracking is conducted by the detection of a track groove and the feedback control of the scanning area based on thus detected position, but the detection error of the tracking groove becomes an obstacle, particularly in a high-speed scanning required for example in the information processing apparatus, because said detection relies on a weak signal such as the tunneling current generated by the close positioning of the probe needle and the specimen. Thus, when the feedback amount is calculated from such detected information, the tracking operation is seriously affected as the feedback system shows instability such as oscillation or overshoot by noises.